Quantitative Relationships Among Golden-Cheeked Warbler Occurrence and Landscape Size, Composition, and Structure

Abstract

The golden‐cheeked warbler (Dendroica chrysoparia) is a federally listed endangered species with an extremely limited breeding range (Edwards Plateau, Tex., USA) and specific habitat requirements. Although localized habitat composition and structure correlate well with golden‐cheeked warbler occurrence and nest location, the effects of landscape composition and structure are largely untested. To investigate landscape‐scale influences on habitat occupancy, we surveyed 202 point locations for golden‐cheeked warbler presence. We used logistic regression to compare the relative influence of 4 landscape‐scale variables (largest patch index, percent of the landscape in woodland, mean‐nearest neighbor, and edge density) measured at 4 spatial scales (3 ha, 12 ha, 50 ha, and 200 ha) in predicting occurrence. The amount of mature juniper‐oak (Juniperus ashei and Quercus spp.) woodland in the landscape was the single most important variable across spatial scales and average values of woodland cover remained stable across scales. Golden‐cheeked warblers occurred in a local habitat only when landscape composition exceeded 40% woodland and the likelihood of occurrence was greater than 0.5 only when landscape composition exceeded 80% woodland. By contrast, common measures of habitat fragmentation, including edge density and mean‐nearest neighbor, were poor predictors of species occurrence across all spatial scales. Our results suggest that golden‐cheeked warblers may be less sensitive to fragmentation then they are to overall habitat loss, which may be due to natural habitat heterogeneity related to the variable terrain. Our results do not preclude a relationship between habitat fragmentation and overall habitat quality as measured by nesting success, survival, and recruitment. While our results hold promise for increasing the reliability of predicting species occurrence, future studies are needed to determine the influence of landscape composition and structure on the ultimate measures of habitat quality. (WILDLIFE SOCIETY BULLETIN 34(2):473–479; 2006)

Amount and Type of Forest Cover and Edge Are Important Predictors of Golden-cheeked Warbler Density

“…We also found strong support for our prediction that proportion of forest cover affected density positively, which is consistent with patterns in Golden-cheeked Warbler occurrence (DeBoer and Diamond 2006, Magness et al 2006, Collier et al 2010, as well as with abundance of other migratory passerines nesting in forest (Flather and Sauer 1996, Howell et al 2000, Thompson et al 2012. A positive relationship between density and proportion of forest cover could be a bird's response to increased quantity of suitable habitat (Whitcomb et al 1981, Temple andCary 1988) or to factors that affect habitat quality, such as microhabitat characteristics (Lynch and Whigham 1984), food availability (Blake 1983, Burke andNol 1998), or changes in levels of nest prédation associated with proportion of forest cover , Robinson et al 1995, Tewksbury et al 1998) and its effect on the abundance and activity patterns of nest predators (Donovan et al 1997, Chalfoun et al 2002.…”

“…Reports of the effect of edge on Golden-cheeked Warbler occurrence have been mixed, with a negative relationship found in some cases (DeBoer andDiamond 2006, Sperry 2007) but not others (Kroll 1980, Magness et al 2006. Density of other passerines nesting in forest also is lower near habitat edges (Kroodsma 1982, Van Horn et al 1995.…”

“…DeBoer and Diamond (2006) found that occurrence was positively associated with larger patches with less edge. Magness et al (2006) assessed occurrence at scales of radii of 100, 200, 400, and 800 m and found that pereent of woodland in the landscape and patch size were the most important variables in predicting occurrence at all scales. Occurrence was positively associated with density of edges at the 100-m scale but negatively associated with it at the larger scales.…”

“…(2) forest-edge density should affect the warbler's density negatively because occurrence is negatively correlated with amount of and distance from edge (DeBoer andDiamond 2006, Sperry 2007) and forest edges affect nest survival negatively (Peak 2007, Reidy et al 2009 (3) patch size should affect density positively because occurrence (DeBoer and Diamond 2006, Magness et al 2006, Collier et al 2010) and reproductive success (Fink 1996, Coldren 1998) are positively correlated with patch size and; (4) proportion of forest cover should positively affect density because the overall amount of forest in the landscape is an important predictor of occurrence (DeBoer and Diamond 2006, Magness et al 2006, Collier et al 2010.…”

Using LiDAR‐derived vegetation metrics for high‐resolution, species distribution models for conservation planning

“…Thus, management for these two species can sometimes be viewed as competing, and clearly requires strategic planning if both species are to be effectively managed. Most research on distributions for both species has focused on coarse landscape metrics, such as patch size, patch configuration, and woody cover in the landscape scale (De Boer and Diamond 2006, Magness et al 2006, Collier et al 2012) providing a foundation for predicting patterns of warbler distribution at coarse resolutions over broad spatial extents. Efforts have been less successful at prediction of vireo distributions using coarse landscape metrics (McFarland et al 2012a, Wilsey et al 2012.…”